HI, I was wondering if there is anyway I can tell what way a house is wired by looking at the wires going into a wall socket, switch or to a pendant light?
Identifying a radial or a ring circuit?
- Thread starter Fony T
- Start date
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The short answer is, unfortunately, no.
Lighting circuits (hence light switches and lights) will virtually never be on a ring circuit.
The only way to be (pretty) sure whether sockets are on a ring or radial circuit would be by looking inside the consumer unit (or 'fuse box/board').
As a matter of interest, why do you want or need to know what type of circuit(s) you have?
Kind Regards, John
Hi John, I appreciate the swift answer.
I'm looking to add an extra socket at one location and another lighting connection to run spotlights from, I was told that the approach was different depending on the way the house is wired.
I've attached an image I took back when the house was being built (taken for posterity purposes) of the wires where the consumer unit is now installed.
I'm looking to add an extra socket at one location and another lighting connection to run spotlights from, I was told that the approach was different depending on the way the house is wired.
I've attached an image I took back when the house was being built (taken for posterity purposes) of the wires where the consumer unit is now installed.
As I said before, the lighting circuit(s) will be radial circuits, not rings - so there's really no issue there.
Adding socket(s) does require knowledge of the type and arrangement of the circuit concerned, but you would probably need an electrician to inspect and test the circuit to be sure of the situation.
I'm afraid that doesn't really help (at least, not me). One would need to know where all those wires ended up going to in the CU in order to even start working out what was going on.
Sorry that I can't be more helpful!
Kind Regards, John
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We have for sockets in the main three systems.
1) The Ring normally wired using 2.5 mm² cable and supplied from a 32 amp fuse/MCB/RCBO.
2) The Radial normally wired using 4 mm² or 6 mm² cable and supplied from a 32 amp fuse/MCB/RCBO.
3) The Radial normally wired using 2.5 mm² cable and supplied from a 20 amp or 16 amp fuse/MCB/RCBO.
So if number 3) easy identified as it is supplied 16 or 20 amp protective device. However the first two are both supplied from 32A protective device, in both cases they can have spurs using 2.5 mm² cable and fused spurs using 2.5 mm² cable or 1.5 mm² cable. A fused spur is really a radial from the main circuit and can have a string of sockets.
I have come to work on a circuit and found it was wired with 4 mm² cable as a radial, however some electrician, and yes it must have been an electrician because of where it was, it would not have been a DIY job, anyway he had clearly thought it was a ring and had broke into the circuit and extended with 2.5 mm² cable so it started with 4 mm² then went to 2.5 mm² and then back to 4 mm² this could result in an overload of the 2.5 mm² section and also if one inspected the 2.5 mm² section one would think it was a ring. Only testing showed it was not a ring. It was with a routine inspection and test the fault was found and the fuse swapped from 32A to 20A until it could be corrected.
We have argued on this forum about the use of a figure of 8 design, in theory had I joined the two 4 mm² cables back together it would have stopped the problem with overload. In fact some times we have what is refereed to as the lollipop system where a heavy cable (6 mm²) takes power to some area like a kitchen then it with something like a double cooker connection unit turns into a ring dedicated to that room. Personally not keen on the idea as it can allow overloads of sockets near the cooker connection unit, but have not found any rule to stop it being used. Use of that system means seeing one cable only connected to a 32A protective device in the consumer unit does not mean at some latter point it turns into a ring.
This is why the paper work is so important, we should have for every installation a "Schedule of Test Results" on this form we have among other things a "Circuit Description" followed by size and type of over current device for each circuit then cable size then if a ring or radial giving also the resistance and then another 6 or so boxes giving more information.
I have one for mothers house rewired not long ago, but my house which I bought new in 1979 never had a "Schedule of Test Results" I have made one out since doing a EICR but there was not one issued buy builder, although he should have done, at that time no one seemed to worry about paper work. Today on change of occupant or every 10 years (England and Wales) which ever the shorter we should get an EICR done, in Scotland for rented property it is law, rest of UK recommended only. I think that applies to Northern Ireland? As with Wales your not same as England and I am not sure how rules differ to England. I know you have some odd systems over there, the Willis hot water system for example not found in rest of UK, also I know your distribution system uses 10kV were rest of UK it's 11kV so there may be systems used there I am unaware of.
The picture looks like commercial premises but also looks quite new, so you may have a "Schedule of Test Results"?
1) The Ring normally wired using 2.5 mm² cable and supplied from a 32 amp fuse/MCB/RCBO.
2) The Radial normally wired using 4 mm² or 6 mm² cable and supplied from a 32 amp fuse/MCB/RCBO.
3) The Radial normally wired using 2.5 mm² cable and supplied from a 20 amp or 16 amp fuse/MCB/RCBO.
So if number 3) easy identified as it is supplied 16 or 20 amp protective device. However the first two are both supplied from 32A protective device, in both cases they can have spurs using 2.5 mm² cable and fused spurs using 2.5 mm² cable or 1.5 mm² cable. A fused spur is really a radial from the main circuit and can have a string of sockets.
I have come to work on a circuit and found it was wired with 4 mm² cable as a radial, however some electrician, and yes it must have been an electrician because of where it was, it would not have been a DIY job, anyway he had clearly thought it was a ring and had broke into the circuit and extended with 2.5 mm² cable so it started with 4 mm² then went to 2.5 mm² and then back to 4 mm² this could result in an overload of the 2.5 mm² section and also if one inspected the 2.5 mm² section one would think it was a ring. Only testing showed it was not a ring. It was with a routine inspection and test the fault was found and the fuse swapped from 32A to 20A until it could be corrected.
We have argued on this forum about the use of a figure of 8 design, in theory had I joined the two 4 mm² cables back together it would have stopped the problem with overload. In fact some times we have what is refereed to as the lollipop system where a heavy cable (6 mm²) takes power to some area like a kitchen then it with something like a double cooker connection unit turns into a ring dedicated to that room. Personally not keen on the idea as it can allow overloads of sockets near the cooker connection unit, but have not found any rule to stop it being used. Use of that system means seeing one cable only connected to a 32A protective device in the consumer unit does not mean at some latter point it turns into a ring.
This is why the paper work is so important, we should have for every installation a "Schedule of Test Results" on this form we have among other things a "Circuit Description" followed by size and type of over current device for each circuit then cable size then if a ring or radial giving also the resistance and then another 6 or so boxes giving more information.
I have one for mothers house rewired not long ago, but my house which I bought new in 1979 never had a "Schedule of Test Results" I have made one out since doing a EICR but there was not one issued buy builder, although he should have done, at that time no one seemed to worry about paper work. Today on change of occupant or every 10 years (England and Wales) which ever the shorter we should get an EICR done, in Scotland for rented property it is law, rest of UK recommended only. I think that applies to Northern Ireland? As with Wales your not same as England and I am not sure how rules differ to England. I know you have some odd systems over there, the Willis hot water system for example not found in rest of UK, also I know your distribution system uses 10kV were rest of UK it's 11kV so there may be systems used there I am unaware of.
The picture looks like commercial premises but also looks quite new, so you may have a "Schedule of Test Results"?
Fony, FYI, this is the problem if you just look at a socket.
On the left is a ring, on the right a radial:
But look at what you'll see at the sockets:
Fony. I assume that what we are talking about is a newish installation?
If that is the case then the completed installation will have come with an Installation Certificate. This will detail the characteristics of each and every circuit.
Do you have this? Post a pic of the test results sheet, if you don't understand it.
If that is the case then the completed installation will have come with an Installation Certificate. This will detail the characteristics of each and every circuit.
Do you have this? Post a pic of the test results sheet, if you don't understand it.
Indeed.
For the OP, even if one looks inside the CU, one cannot necessarily be sure.
If there is only one cable connected to the MCB/fuse for the circuit then (unless somebody has done something very wrong, non-compliant and potentially very dangerous) the circuit 'must' be a radial (a ring has two ends, both of which should both be connected to the same MCB/fuse).
However, if there are two (or more) cables connected to the MCB/fuse, then it could be either radial or ring. It is very likely to be a ring, but it could also be a radial with branch(es) originating in the CU.
As I said to the OP, short of exposing and tracing all the wiring, the only real way to be sure is to undertake some tests, and that usually requires an electrician with the appropriate kit.
Kind Regards, John
You mean a spur from a spur?
No. I made a typo which I have now corrected. Thanks.
You can if you are really certain (crystal ball?) that you are not spurring from a unfused spur from a ring final that already has a (non-compliant) further 'spur' originating from it. The only absolutely certain (without tracing and/or testing the circuit) situation exists when one adds a socket from the final socket on a radial.
Kind Regards, John
In fact, the point I was trying to make was actually incorrect. I was actually thinking of the OP's situation, in which one does not know whether the circuit was a ring or radial, but in that situation one obviously does not know that a socket with just one cable is 'the end of a radial' (or end of a branch of a radial) - it could just as easily be a spur from a ring.
However, I don't think your suggested modification of my statement is, without qualification, necessarily correct, either. A 4mm² radial can have a 2.5mm² 'unfused spur', with exactly the same restrictions as with a ring final - so the same risk of (unacceptably) 'spurring from a spur' exists as with a ring final.
Kind Regards, John
I would never occur to me to ever, ever, ever use an undersized cable for a branch on a radial.
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